Co-pending application, Ser. No. 291,483, describes a mail machine for high speed processing of mixed mail, which includes unsealed as well as sealed envelopes. The mail flow in such a machine typically begins at a hopper where the incoming mail to be processed is stacked. The main flow path continues through a singulator, which separates individual mail pieces from the stack for serial processing. Following the singulator, the envelopes are caused to flow along the main path through a moistener which moistens the glue on the flaps of the unsealed envelopes and then seals the envelopes, and thereafter along the main path to a weigher and printer including a postage meter. The machine is intended to handle mixed mail, by which is meant unsealed envelopes with the flaps open in the position for moistening, unsealed envelopes with the flap closed and which has to be opened by the machine to the moistening position, and already-sealed envelopes.
In this environment, it is important to detect the presence of mis-sealed envelopes, that is, envelopes in which the sealed edge, instead of lying flat, may protrude outwardly or display other undesired anomalous leading edge states. If allowed to continue along the main flow path, such mis-sealed envelopes may jam the machine.